Securing subfloor over a concrete pad

Hi,

I'm working on a enclosed porch (breezeway, 3-season room, etc), that had a concrete pad as a floor. I put down pressure treated 2x3's, with PL400 and Ramset nails. I then put 3/4 OSB down on top. My plan was to cover with cement board and then put ceramic tile on top.

The issue is that in a few places, you can feel a little bit of movement in the floor. The OSB and sleepers are glued and screwed together, which makes me think that the concrete and sleeper are not fully attached. Knowing that I need to have the floor be solid before putting down tile, I'm not sure what I can do, now that the OSB is pretty much solidly attached to the sleepers.

My first thought is to try out some long Tapcom's, but I've never had good luck with getting a good hold with them. I could also try firing more ramset nails but with the sleeper, they would only penetrate about an inch into the concrete, and that might not be good enough. Would the 1/4" cement board on top of the OSB stiffen the floor up enough, if these two options don't work?

Securing subfloor over a concrete pad

Your entire plan is seriously flawed and will not work. You should remove and install the ceramic tile on the slab, or over a crack isolation membrane such as Ditra or Noble.

Jaz

The concrete slab was ice-cold in the winter (Ohio), so I wanted to insulate the floor. There is ridgid foam insulation between the sleepers to act as both a vapor barrier and insulation. Radiant heat flooring was not an option, as we're not looking to stay here long-term. It sounds like the Ditra is perfect for my application, from a movement perspective, and because a sunroom will experience more temperature swing, and that could allow movement.